p-Substrate Partially Inverted Buried Heterostructure Distributed Feedback Laser Diode Performance Improvement by Inserting Zn Diffusion-Stopping Layer

The leakage current mechanism of p-substrate partially inverted buried heterostructure (PPIBH) distributed feedback laser diode (DFB-LD) grown on a p-InP substrate was studied in equivalent circuit simulations and experiments. The results showed that the p-InP buffer layer, which adheres to the active layer, has an important role and increasing its carrier concentration reduces the leakage current. High doping in the buffer layer caused the LD characteristics to deteriorate, which was caused by Zn diffusion into the active layer from the substrate. To prevent this diffusion, an undoped InP as a Zn diffusion stopping layer inserted between the buffer layer and the substrate was proposed. The LD with this layer showed superior characteristics with a second intermodulation distortion of -50 dBc and an R d of 2.9 Ω.